Hoisting slings have been known for many years and are useful in providing a connecting link between a chain hoist, winch or crane and an object to be hoisted or lifted.
Such slings characteristically feature an elongate flexible lifting element such as a rope, cable, strap or chain having a hook secured to one or both of its ends for hooking onto an object to be hoisted.
In some instances, such slings feature a hook secured to one end and an eyelet secured to the opposite end that can be engaged by a hook attached to the winch or crane being used to hoist the object.
In other instances, such slings have featured a plate or bracket at one end that enables the end of the lifting element to be secured by bolts or the like to the object to be hoisted.
Early examples of a sling hoist having lifting elements having a hook at one end and an eyelet at the other end are disclosed in U.S. Pat. Nos. 1,755,854; 1,918,007; 2,356,146; and 2,541,449, the disclosures of which are incorporated hereby by reference.
Examples of sling hoists whose lifting elements are adapted to be secured to the object to be lifted by a bolt or the like is disclosed in U.S. Pat. No. 2,315,146, the disclosure of which is incorporated herein by reference.
Examples of hooks operative to be used in sling hoists are disclosed in U.S. Pat. Nos. 200,510 and 264,530, the disclosures of which are incorporated herein by reference.
In two instances since the late eighteen hundreds, a pivotal cross bar has been employed for insertion through an opening through an object and thence pivoting to bridge across the hole to prevent the removal thereof. In neither instance is disclosed or suggested that the pivoting principle might be adapted for use in connection with sling hoists. In the first instance, a wagon bolt employed a guard (d) pivotally mounted on the end of a rigid shaft (a) is disclosed in U.S. Pat. No. 109,640, the disclosure of which is incorporated herein by reference. Here, the pivotal shaft is not secured to the end of an elongate flexible lifting element such as rope, cable, strap or chain but rather to a wooden shaft and no suggestion is made that such concept might be adaptable to sling hoists.
In the second instance, a safety line id disclosed in U.S. Pat. No. 3,332,118, the disclosure of which is incorporated herein by reference. Here, however, the pivotal member requires a two cable connection to the cross bar (3) that itself is pivotally mounted at one end and may not proximate the center as is the case for the present invention.
In contrast to the prior art hereinbefore described, the hoisting sling of the present invention in one embodiment employs a pivot assembly that is economical to manufacture and simple in design by featuring a cross bar that is pivotally mounted proximate the center and can be easily inserted through an opening through an object and then pivoted to a position causing the cross bar to bridge across the opening to enable the lifting element to commence the task of hoisting the object.
In yet another embodiment of the invention, the pivot assembly cross bar is a two-piece cross bar with each piece having one end pivotally mounted to the pivot assembly and which may further include at least one biasing member operative to bias the pieces away from each other in the manner of a toggle bolt or the like.
In still another embodiment a locking pin is included to prevent the cross bar from being inadvertently withdrawn from the opening through the object.